1. Field of the Invention
The present invention relates to a method of measuring temperature of a tunnel magnetoresistive effect (TMR) element used as, for example, a read head element of a thin-film magnetic head.
2. Description of the Related Art
In a thin-film magnetic head provided with a TMR read head element, it is sometimes requested to evaluate the temperature of the TMR read head element in a state that the head is actually mounted on an apparatus. For instance, the temperature of the TMR read head element is affected by environmental temperature, generation of heat due to a heater provided inside, generation of heat due to write current flowing through a write head element, and a cooling effect due to air flow caused by flying above a surface of a rotating magnetic disk, and therefore the actual temperature of the TMR read head element cannot be evaluated unless the head is actually mounted on a magnetic disk drive apparatus such as a hard disk drive (HDD) apparatus and the magnetic disk is rotated. Particularly, the cooling effect due to air flow caused by flying above the magnetic disk surface is remarkably affected by, for example, the shape of an air bearing surface (ABS) of the thin-film magnetic head, and therefore accurate temperature cannot be detected unless the head is actually mounted on the HDD apparatus with the magnetic disk rotated so as to be flied.
As a typical technique for detecting the temperature of a read head element in a state that the thin-film magnetic head is actually mounted on an HDD apparatus, there has been a method of detecting the temperature by utilizing temperature dependency of element resistance of the read head element. In this method, temperature coefficient of the element resistance is obtained in advance, and the element temperature is obtained using the temperature coefficient based on the actually obtained element resistance.
However, a problem arises when applying this method to TMR read head elements, while this method is effective in usual anisotropic magnetoresistive effect (AMR) read head elements, and giant magnetoresistive effect (GMR) read head elements. That is, as is well known, the TMR read head element has a tunnel barrier layer that is an electrically insulating layer, and temperature coefficient of the element resistance is very small. Therefore, it has been difficult to obtain the element temperature from the temperature coefficient by measuring the element resistance of the TMR read head element, and further the temperature has not been detected accurately even when it is obtained.